Nature of the Band Gap and Origin of the Conductivity of PbO2 Revealed by Theory and Experiment

作者：Scanlon David O^*; Kehoe Aoife B; Watson Graeme W; Jones Martin O; David William I F; Payne David J; Egdell Russell G; Edwards Peter P; Walsh Aron

来源：Physical Review Letters, 2011, 107(24): 246402.

DOI：10.1103/PhysRevLett.107.246402

Lead dioxide has been used for over a century in the lead-acid battery. Many fundamental questions concerning PbO2 remain unanswered, principally: (i) is the bulk material a metal or a semiconductor, and (ii) what is the source of the high levels of conductivity? We calculate the electronic structure and defect physics of PbO2, using a hybrid density functional, and show that it is an n-type semiconductor with a small indirect band gap of similar to 0.2 eV. The origin of electron carriers in the undoped material is found to be oxygen vacancies, which forms a donor state resonant in the conduction band. A dipole-forbidden band gap combined with a large carrier induced Moss-Burstein shift results in a large effective optical band gap. The model is supported by neutron diffraction, which reveals that the oxygen sublattice is only 98.4% occupied, thus confirming oxygen substoichiometry as the electron source.

• 出版日期2011-12-7